<template>
    <div class="s-canvas">
        <canvas id="s-canvas" :width="contentWidth" :height="contentHeight"></canvas>
    </div>
</template>

<script>
    export default {
        name: "el-identify-code",
        props: {
            identifyCode: {
                type: String,
                default: '1234'
            },
            fontSizeMin: {
                type: Number,
                default: 16
            },
            fontSizeMax: {
                type: Number,
                default: 40
            },
            backgroundColorMin: {
                type: Number,
                default: 180
            },
            backgroundColorMax: {
                type: Number,
                default: 240
            },
            colorMin: {
                type: Number,
                default: 50
            },
            colorMax: {
                type: Number,
                default: 160
            },
            lineColorMin: {
                type: Number,
                default: 40
            },
            lineColorMax: {
                type: Number,
                default: 180
            },
            dotColorMin: {
                type: Number,
                default: 0
            },
            dotColorMax: {
                type: Number,
                default: 255
            },
            contentWidth: {
                type: Number,
                default: 112
            },
            contentHeight: {
                type: Number,
                default: 45
            }
        },
        methods: {
            // 生成一个随机数
            randomNum (min, max) {
                return Math.floor(Math.random() * (max - min) + min)
            },
            // 生成一个随机的颜色
            randomColor (min, max) {
                let r = this.randomNum(min, max);
                let g = this.randomNum(min, max);
                let b = this.randomNum(min, max);
                return 'rgb(' + r + ',' + g + ',' + b + ')'
            },
            drawPic () {
                let canvas = document.getElementById('s-canvas');
                let ctx = canvas.getContext('2d');
                ctx.textBaseline = 'bottom';
                // 绘制背景
                ctx.fillStyle = this.randomColor(this.backgroundColorMin, this.backgroundColorMax);
                ctx.fillRect(0, 0, this.contentWidth, this.contentHeight);
                // 绘制文字
                for (let i = 0; i < this.identifyCode.length; i++) {
                    this.drawText(ctx, this.identifyCode[i], i)
                }
                this.drawLine(ctx);
                this.drawDot(ctx)
            },
            drawText (ctx, txt, i) {
                ctx.fillStyle = this.randomColor(this.colorMin, this.colorMax);
                ctx.font = this.randomNum(this.fontSizeMin, this.fontSizeMax) + 'px SimHei';
                let x = (i + 1) * (this.contentWidth / (this.identifyCode.length + 1));
                let y = this.randomNum(this.fontSizeMax, this.contentHeight - 5);
                var deg = this.randomNum(-45, 45);
                // 修改坐标原点和旋转角度
                ctx.translate(x, y);
                ctx.rotate(deg * Math.PI / 180);
                ctx.fillText(txt, 0, 0);
                // 恢复坐标原点和旋转角度
                ctx.rotate(-deg * Math.PI / 180);
                ctx.translate(-x, -y)
            },
            drawLine (ctx) {
                // 绘制干扰线
                for (let i = 0; i < 8; i++) {
                    ctx.strokeStyle = this.randomColor(this.lineColorMin, this.lineColorMax);
                    ctx.beginPath();
                    ctx.moveTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight));
                    ctx.lineTo(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight));
                    ctx.stroke()
                }
            },
            drawDot (ctx) {
                // 绘制干扰点
                for (let i = 0; i < 100; i++) {
                    ctx.fillStyle = this.randomColor(0, 255);
                    ctx.beginPath();
                    ctx.arc(this.randomNum(0, this.contentWidth), this.randomNum(0, this.contentHeight), 1, 0, 2 * Math.PI);
                    ctx.fill();
                }
            }
        },
        watch: {
            identifyCode () {
                this.drawPic();
            }
        },
        mounted () {
            this.drawPic();
        }
    }
</script>

<style scoped>

    .s-canvas{
        display: inline-block;
        vertical-align: middle;
        height: 45px;
    }

</style>
